Starfish saponins, 52. Chemical constituents from the starfish Echinaster brasiliensis

Two new polyhydroxylated steroidal glycosides from the starfish Culcita novaeguineae

The chemical constituent investigation on the starfish Culcita novaeguineae resulted in the isolation of two new polyhydroxylated steroidal glycosides and two known ones. The new compounds were identified as (25S)-3-O-(2-O-methyl-β-D-xylopyranosyl)-26-O-(β-D-xylopyranosyl)-cholest-4-ene-3β,6β,7α,8,15α,16β,26-heptaol (1) and (25S)-3-O-(2-O-methyl-β-D-xylopyranosyl)-26-O-(β-D-xylopyranosyl)-cholest-4,24(28)-diene-3β,6β,7α,8,15α,16β,26-heptaol (2) and the known compounds were determined as linckosides I and H (3-4). The structures of the isolated compounds were elucidated on the basis of extensive spectroscopic studies and chemical evidence. In addition, the cytotoxicity of the two new compounds against human glioblastoma cell lines U87, U251 and SHG44 was evaluated by MTT method.

Asterosaponins: Structures, Taxonomic Distribution, Biogenesis and Biological Activities

Asterosaponins are a class of steroid oligoglycosides isolated from starfish with characteristic structures and diverse biological activities. In this review, we have attempted to combine the most important data concerning asterosaponins and give a list of these secondary metabolites with their structural peculiarities. The purpose of this review is to provide a brief but as complete as possible principal information about their chemical structures, taxonomic distribution in the marine environment, distribution in different geographical areas and depths, some properties, biological activities, and functions. Some other rare steroid metabolites from starfish, closely related in structures and probably biogenesis to asterosaponins, are also discussed.

New Neuritogenic Steroid Glycosides from the Vietnamese Starfish Linckia Laevigata

Two new steroid glycosides, linckosides L1 (1) and L2 (2), were isolated, along with the previously known echinasteroside C (3) from the ethanolic extract of the Vietnamese blue starfish, Linckia laevigata. The structures of the new compounds were elucidated by spectroscopic methods (mainly 2D NMR) and chemical transformations. Lifetime observations and analyses of silver impregnated preparations on the culture of neuroblastoma C-1300 cells showed that glycosides 1, 2, and 3 are capable of inducing neuronal differentiation similar to that of neurotrophins and of enhancing substantially the neuritogenic activity of NGF.

Anthraquinone and Butenolide Constituents from the Crinoid Capillaster multiradiatus

Seven anthraquinones including two new compounds namely capillasterquinones A and B (1 and 2) and one new butenolide namely capillasterolide (8) were isolated and structurally elucidated from the crinoid Capillaster multiradiatus. The inhibitory effect of compounds 1-8 on lipopolysaccharide (LPS)-induced nitric oxide (NO) production as well as inhibition of 1 on expressions of inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2) proteins in RAW264.7 cells were also evaluated. As the obtained results, capillasterquinone A (1) showed strong NO production inhibitory activity with an IC₅₀ of 5.89±0.11 µM. In addition, compound 1 reduced the LPS-induced iNOS and COX-2 expressions in a dose-dependent manner.

Cytotoxic Polyhydroxysteroidal Glycosides from Starfish Culcita novaeguineae

Four new polyhydroxysteroidal glycosides—culcinosides A–D (1, 2, 4, and 7)—along with three known compounds—echinasteroside C (3), linckoside F (5), and linckoside L3 (6)—were isolated from the ethanol extract of starfish Culcita novaeguineae collected from the Xisha Islands of the South China Sea. The structures of new compounds were elucidated through extensive spectroscopic studies and chemical evidence, especially two-dimensional (2D) NMR techniques. The cytotoxicity of the new compounds against human glioblastoma cell lines U87, U251, and SHG44 were evaluated.

Formation of the steroidal C-25 chiral center via the asymmetric alkylation methodology

A novel approach for the preparation of steroids containing a chiral center at C-25 is reported. The key stereochemistry inducing step was asymmetric alkylation of pseudoephenamine amides of steroidal C-26 acids. The reaction proceeded with high diastereoselectivity (dr > 99 : 1). The developed methodology was successfully applied to the synthesis of (25R)- and (25S)-cholestenoic acids as well as (25R)- and (25S)-26-hydroxy brassinolides.

Chemical constituents and bioactivities of starfish

Starfish have been the research topic in many chemical and pharmacological laboratories due to their complex secondary metabolites and diverse bioactivities. The aim of this review is to provide an up-to-date review on the chemistry and bioactivity of compounds isolated from all kinds of starfish to illustrate the chemodiversity and biological significance of these constituents, along with their geographical distribution where it is discernible.

Leishmanicidal activity of Echinaster (Othilia) echinophorus crude extract

In this study, a methanolic extract from Echinaster (Othilia) echinophorus was evaluated for activity against Leishmania amazonensis. The extract showed activity against the promastigote and amastigote forms with IC50 values of 62.9 and 37.5 μg.mL-1 respectively. This extract showed a moderate toxicity on macrophages from BALB/c mice. A dose of 100 mg/kg/day was effective when administered during 15 days by intraperitoneal route to BALB/c mice infected experimentally.

Steroidal monoglycosides from the Far Eastern starfish Hippasteria kurilensis and hypothetic pathways of polyhydroxysteroid biosynthesis in starfish

Five new steroidal monoglycosides, kurilensosides E (1), F (2), G (3), H (4) and 15-O-sulfate of echinasteroside C (5) were isolated along with the previously known echinasteroside C (6) from the alcoholic extract of the Far Eastern starfish Hippasteria kurilensis collected near Kuril Islands. Compounds 1-3 were determined to contain unusual polyhydroxysteroidal aglycons lacking 6-hydroxy group. Aglycon moiety of kurilensoside H (4) was shown to be the first case of marine polar steroids containing 4,5-epoxy functionality. Hypothetic pathways of the biosynthesis of polyhydroxysteroids and related glycosides in starfish and the existence of the late C-6 oxidation pathway in H. kurilensis are discussed.

Structure-activity relationships of novel neuritogenic steroid glycosides from the Okinawan starfish Linckia laevigata

Six new steroid glycosides, linckosides F-K, and a related metabolite were isolated from the Okinawan blue starfish Linckia laevigata as mimics or enhancers of nerve growth factor (NGF). Their structures and stereochemistry were elucidated by spectroscopic methods and chemical derivatization. Structure-activity relationships suggest that both a carbon branch modified by a pentose at the side chain and 2'-O-methylxylopyranose at C-3 of the aglycon are important for neuritogenic activity.

Marine natural products

This review covers the literature published in 2004 for marine natural products, with 693 citations (491 for the period January to December 2004) referring to compounds isolated from marine microorganisms and phytoplankton, green algae, brown algae, red algae, sponges, coelenterates, bryozoans, molluscs, tunicates and echinoderms. The emphasis is on new compounds (716 for 2004), together with their relevant biological activities, source organisms and country of origin. Biosynthetic studies (8), and syntheses (80), including those that lead to the revision of structures or stereochemistries, have been included.

Anti-adhesive glycoproteins in echinoderm mucus secretions

Marine invertebrates produce a large variety of mucus secretions which are rich in glycoproteins. As part of our studies of natural antifouling mechanisms, mucus secretions from the starfish Marthasterias glacialis and Porania pulvillus and the brittlestar Ophiocomina nigra have been used to characterise the structure and function of some of the glycoproteins present in these secretions. Mucus was collected from all three species and fractionated by size exclusion chromatography. A high molecular weight glycoprotein fraction was collected from each species. Monosaccharide analysis and FTIR demonstrated a composition consistent with a mucin-type glycoprotein. The mucin from M. glacialis and O. nigra inhibited in vitro bacterial adhesion in a dose-dependent manner. In contrast, the mucin from P. pulvillus promoted bacterial adhesion in a dose-dependent manner. All of the mucins inhibited the adhesion of human neutrophils to cultured human vascular endothelial cells (HUVECs) and had no anticoagulant activity. The mucins described here have adhesion-regulating functions that may have a role in the antifouling or feeding mechanisms of the organisms that produce them. These mucins may also be of therapeutic value through their ability to regulate human neutrophil adhesion or bacterial adhesion.

Characterization of antimicrobial agents extracted from Asterina pectinifera

The extracts from the starfish Asterina pectinifera obtained using various organic solvents and distilled water were tested for their antimicrobial activities against fungi and yeasts. The methanol and water extracts were found to be the most active and Aspergillus spp. and Cryptococcus neoformans proved to be sensitive species. The extracts are polar, stable to a wide range of pH and a high temperature, and possess a very distinctive UV spectrum. The colour reactions for functional groups of antimicrobial substances indicate the presence of some distinctive chemical properties common to steroidal oligoglycosides which results suggest that the antimicrobial activity is due to structures common to steroidal oligoglycosides.

Steroid and triterpenoid oligoglycosides of marine origin

Saponins have been considered for a long time typical metabolites of plant origin. It has been only in the last two decades that the world-wide investigation of marine organisms as sources of new bioactive metabolites disclosed the wide distribution of these molecules also among marine animals. Today saponins are recognized as the most common characteristic metabolites in two classes of the phylum Echinodermata (Holothuroidea and Asteroidea). Furthermore, several steroid and triterpenoid oligoglycosides have been isolated from different species of marine sponges, more rarely Anthozoans, and also from fishes of the genus Pardachirus, where they have been shown to act as shark repellents. This communication offers a general view of the distribution of steroid and triterpenoid oligoglycosides among marine organisms and focuses on a number of recent examples to discuss structural characteristics, biological activities, and methods of investigation.